Model railroad locomotives exist in various sizes. Serious model railroaders operate these locomotives in all scales from the smallest N gauge to the largest G gauge. A locomotive may have a length greater than one foot and a weight of several pounds in the larger scales. And larger models are often used in a sight-seeing park such as a zoo. Currently, the desire to have these model locomotives operate in the same fashion as full size locomotives is thwarted because of drive motor size limitations with respect to the various available model locomotives.
Of particular importance is the manner in which these locomotives operate from a standstill to acquire an equivalent scale operation of a full-size train. The model railroader is always looking for a more realistic looking operation of the model locomotive. But because of space limitations, the motors used to drive existing model locomotives, usually called "can" motors because they look like a small can, are very small and weak.
The known electric drive motors range from about 1/2 inch to about 11/2 inches in diameter with a length from about 1 inch to about 13/4 inches. These small direct current (DC) electric motors have a power range from about 0.002 to about 0.009 horsepower with a rotational speed range for the rotatable power shaft of the motor in the range of about 7,000 to about 16,000 revolutions per minute (rpm). The locomotive motor power shaft is connected to a drive shaft that rotates a worm and worm gearset connected to rotate the locomotive drive wheels also known as drivers. The normal installation uses a 31:1 worm and worm gear ratio to produce one revolution of the drivers for 31 revolutions of the drive shaft to provide sufficient power once the motor is running. The problem with these existing locomotives, however, is that slow realistic starts and very low speed control are difficult to achieve without stalling the drive motor.
Attempts have been made to effect the noted desired results by using pulsating current to operate the electric motors and/or by using technological advances such as skewed armatures in the motor construction itself. Yet at slow operating speeds, the armature of the electric motor turns very slowly and is thus subject to stalling from any unexpected load increase or any slight bind in the locomotive drive mechanism. Moreover, operating these motors at very slow speeds under a load for more than short time periods may soon overheat the motor causing possible motor damage.
The known motors used to drive these locomotives require 11/2 to 2 volts to start the motor running for rotating a driven shaft coupled to rotate the locomotive drivers. Known locomotive drivers will not rotate on track provided until there is enough power input to the worm and worm gearset to move currently available locomotives along the track. Problems often occur when increasing electric power to the DC motor to increase the rotational speed of the motor and drive shaft. The model railroad locomotive may give a lunging or uneven thrust movement and its motor may ultimately stall. Thus, it is extremely difficult to achieve the desired result of a realistic slow motion start without stalling the locomotive drive motor or without the locomotive producing a lunging or thrusting movement because of a lack of a continuous, adequate power supply to the locomotive drive wheels.
The mechanism of the present invention used to drive scale model locomotives would be modified in each of the other potential uses for the physical and mechanical characteristics of the particular item.
U.S. Pat. Nos. 4,234,164 and 4,721,083 show different systems for producing a stall preventative feature in the power transmission train for a motor. Neither of these prior art systems are operable to achieve the results achieved in the power transmission system of the current invention.
U.S. Pat. No. 4,676,121 shows a planetary gear mechanism used in conjunction with a flywheel for producing inertia moment of the flywheel during idling. This configuration, however, is not equivalent to the structure of the power transmission system disclosed herein.